Tarnish preventive composition

ABSTRACT

A TARNISH PREVENTIVE METAL POLISH COMPOSITION WHEREIN IN A CONVENTIONAL METAL POLISH THERE IS INCLUDED 1% TO 10% BY WEIGHT DITHIO-BIS HIGHER ALKYL ESTER OF FATTY ACID AND 0.2% TO 2% BY WEIGHT ALKYL POLYOXYETHYLENE THIOETHER. THE METAL ARTICLE HAVING THEREON A TARNISH-RESISTANT SURFACE FILM OF DITHIO-BIS HIGHER ALKYL ESTER OF FATTY ACID.

United States l atent 3,758,315 TARNISH PREVENTIVE COMPOSITION Thomas P. Wright, Keene, NJFL, and John W. Rafferty,

Marhlehead, Mass, assignors to J. A. Wright & Company, Keene, N.H.

No Drawing. Continuation of abandoned application Ser. No. 602,524, Dec. 19, 1966. This application Dec. 1, 1970, Ser. No. 94,629

Int. Cl. C08l1 9/100; C09f; (309g US. Cl. 106-8 8 Claims ABSTRACT OF THE DISCLOSURE A tarnish preventive metal polish composition wherein in a conventional metal polish there is included 1% to 10% by weight dithio-bis higher alkyl ester of fatty acid and 0.2% to 2% by weight alkyl polyoxyethylene thioether. The metal article having thereon a tarnish-resistant surface film of dithio-bis higher alkyl ester of fatty acid.

This application is a continuation of application Ser. No. 602,524, filed Dec. 19, 1966, now abandoned.

It is well known that a number of metals commonly used for ornamental or utilitarian purposes have a propensity for tarnishing. This unattractive discoloration is also known to be due to the presence of various reactive substances, such as oxygen, sulfides, etc., in the atmosphere. To attain the characteristic brightness of the metal surface, it is necessary to polish the metal surface and remove this film of tarnish. However, as soon as the surface of the metal was cleaned and polished, a new surface was presented and left unguarded and unprotected against a renewed attack by the deleterious substances in the atmosphere. Unfortunately, it is the very removal of the tarnish film that promotes a more vigorous action against the metal surface, since the tarnish film, intact prior to polishing, in some small way did slow further tarnishing. Consequently, it has been necessary to polish the metal surfaces repeatedly to obtain the clarity and shine desired on metal surfaces.

In an effort to overcome some of the deficiencies of prior metal polishes, metal polish compositions having some tarnish preventive characteristics have recently been made known in the art. For instance, a tarnish preventive silver polish is disclosed in US. Reissue Pat. No. 24,818, to Murphy, and Prior et al., No. 3,248,235, discloses a tarnish preventive composition for copper-containing surfaces. Both patents, however, disclose and are limited to the use of aliphatic mercaptans. The mercaptans as a class of compounds are generally considered to have offensive odors and are easily oxidized with a loss in potency during storage, especially when compounded into a package that may be opened and used intermittently.

It is the object of the present invention to provide a new composition for cleaning metal surfaces which possesses the ability both to polish the metal and leave a thin surface film as a residue which protects the metal from tarnishing for a substantial period of time.

Another object of the present invention is the provision of a metal polish composition which may be easily and simply applied to metal surfaces and will simultaneously polish the surface and provide a tarnish preventive coatlhis invention also has as an object the provision of a metal polish composition which includes a tarnish preventive compound and a wetting agent which promotes the application of the tarnish preventive to the metal surface.

A further object of the present invention is the provision of a wetting agent which assists and promotes the cleaning of the metal surface to permit the formation of the tarnish preventive film on the metal surface.

ice" Another object of the present invention is the provision of a tarnish preventive compound particularly adapted to prevent the tarnishing of silver-containing surfaces.

These and other objects and advantages of the present invention will become apparent to those skilled in the art from the following description.

Briefly, the present invention is directed to a tarnish preventive composition and also to the metal article so protected by the tarnish preventive film. The composition includes an alkyl dithio-bis alkyl ester of lower fatty acids as the tarnish preventive agent, and an alkyl polyoxyethylene thioether as a particular wetting agent having the characteristic of promoting the application of the tarnish preventive agent to the metal surface. The invention also contemplates the addition of optional ingredients, such as the alkylphenyl polyethoxy ethanol as a wetting agent to promote the cleaning of the metal surface, and an abrasive to assist in rapidly exposing a clean metal surface for receiving the tarnish preventive agent and a viscosity controlling agent to vary the consistency of the final product.

In accordance with the present invention, the tarnish preventive agent is a dithio-bis alkyl ester of lower fatty acid (DTE) having the generic formula:

The alkyl radicals forming the esters are preferably selected from those higher in the aliphatic series, particularly those having 8 to 20 carbon atoms. In particular it has been found that the stearyl group produces excellent tarnish preventive results.

The fatty acid portion of the DTE tarnish preventive may be selected from the lower fatty acids, particularly those having 2 to 5 carbon atoms. Within this group it has been found that the acetic and propionic acids having 2 and 3 carbon atoms, respectively, are particularly suitable. Within the preferred group the propionic acid derivative is notable for its ease of dispersion and handling and for the long protection afforded the metal surface.

The amount of the disulfide esters can vary substantially between 1% and 10% by weight, but preferably should be between 3% and 5% by weight of the total composition. The amount of the disulfide ester tarnish preventive is to some extent dependent upon the amount and type of the abrasive that may optionally be added to the metal polish composition. For instance, if the abrasive content is high, the tarnish preventive agent must also be in the high range, in order to protect immediately the area exposed by the abrasive. With a high or harsh abrasive content, the protective layer formed by the tarnish preventive is removed as rapidly as it is formed, so the higher amount of anti-tarnish compound is needed to insure the presence of active ingredients to react with the cleaned metal. With a low abrasive content the amount of the tarnish preventive may be in the lower range; however, as it should be readily apparent, the cleaning of the metal surface will require greater time with the lower abrasive content.

The wetting agent, found to be an important aspect of the present invention, is the alkyl polyoxyethylene thioether, in which the alkyl group may be selected from the range of 6 to 24 carbon atoms.

This thioether is a nonionic wetting agent and as such has been found to assist in maintaining the DTE tarnish preventive dispersed in the polish composition. It is theorizedbut not as yet established-that the thioether wetting agent orients the disulfide moiety of the DTE molecule towards the metal surface. With respect to a silver surface, it is again theorized that there is some form of reaction or combination which takes place between the disulfide ester and the silver to provide a strong and essentially impervious and substantially unreactive film on the surface of the silver to guard the more reactive silver from the deleterious and tarnishproducing agents in the atmosphere.

It has been found that the silver surface has a brighter appearance and is more easily protected for a longer period of time through the presence of the thioether with the DTE ester tarnish preventive. it is again theorized though not established-that the thioether remains on the silver surface to assist in providing the resistant barrier against tarnish producing agents. The amount of the thioether wetting agent may vary between 0.2% and about 3.5%, but generally is used in an approximate amount of 1% by weight.

Optionally, a further wetting agent, also of the nonionic variety, such as the alkyl phenylpolyethoxy ethanol, may be added to the composition, along with the optional abrasive. The alkyl radical of this optional Wetting agent may have from 6 to 24 carbon atoms. Of particular usefulness is the wetting agent, isooctylphenyl polyethoxyethanol. The number of ethoxy groups in the alkylphenyl polyethoxyethanol is not critical, but should be greater than 2. The amount of this wetting agent when utilized is about 0.1% to 3%, and preferably about 1%.

The abrasive preferred in accordance with the present invention is a diatomaceous earth which is soft enough to subdivide before scratching the metal surface, particularly a silver surface. Other abrasives, While not preferable, may be utilized, such as the finely divided silicas, clays, chalks, and the like. The amount of the abrasive can vary substantially and may be from 5% to 25% by weight of the polish composition. The preferable amount is from to As previously stated, there is an inter-relationship between the desired amount of abrasive and the amount of tarnish preventive agent. Accordingly, when the preferred amount of abrasive is used, the stated preferred amount of tarnish preventive agent of 3% to 5% will provide excellent cleaning and polishing and will assure sufficient tarnish preventive to protect the newly formed bright surface.

Further optional ingredients may be added in accordance with the present invention, such as a viscosity controller. This ingredient has not been found to alter the functionality of the protection, but does provide a consistency which may be variable in accordance with the desires of the user. Various viscosity controllers may be utilized; however, in accordance with the present invention, the preferred and particularly desirable viscosity controllers are the polyethylene glycols and their derivatives, which are preferably solid at room temperatures and have a molecular weight of greater than 500. Among the derivatives found acceptable are those having a hydroxyl group on one end and the other end terminating with the methyl ether moiety. These alkoxy polyethylene glycols are somewhat more compatible with hydrocarbons than the corresponding polyethylene glycol, are water soluble, and further have been found to contribute to the wetting and cleaning of the metal surface. The polyethylene glycols of 6000 molecular weight that have been cross-linked through reaction with a difunctional molecule (epoxy, diisocyanate, or glyoxal, for example) in order to obtain molecular weights in excess of 20,000 are also useful as viscosity modifiers. The amount of the viscosity controller can vary substantially; however, it may be used in amounts between 1% and and preferably, when using a polyethylene glycol of 4000- 6000 molecular weight, approximately 10%. The amount of the polyethylene glycol derivative is primarily dictated by the desired consistency of the final product.

Other viscosity modifiers may also be used such as the water soluble cellulose ethers, which include the hydroxymethyl cellulose ethers and the hydroxyethyl cellulose ethers and the like. A number of natural water dispersible gums, such as algin and algin derivatives,

gum arabic, locust bean gum, etc., can also be used to obtain the same viscosity or anti-settling properties. Inorganic thickeners, such as bentonite and other clays, should also be included. In general, these materials supply more efiicient viscosity control because small amounts (0.5% to 3%) will produce the desired texture. They do not modify the solvent character of water, particularly during the incorporation of the DTE in a warm mixture. Thus, although other thickeners may be used, a polyglycol is preferred for the dissolving and dispersing characteristics it possesses with respect to the DTE. Additionally, the glycols have been found to be easier to wash off the metal than other thickeners.

Typical formulations of the composition in accordance with the present invention are as follows:

EXAMPLE 1 Parts by wt. Water 6O Diatomaceous earth 10 Polyethylene glycol (4000 M.W.) 10 Dithio-bis stearyl propionate 3 Nonyl polyoxyethylene thioether 3 Isooctylphenylethoxy ethanol 1 EXAMPLE 2 Parts of wt.

Water 60 Diatomaceous earth l5 Polyethylene glycol (6000 M.W.) 12 Dithio-bis stearyl propionate 5 Nonyl polyoxyethylene thioether 1 Isooctylphenylethoxy ethanol /2 EXAMPLE 3 Parts of wt.

Water 72 Diatomaceous earth 10 Methoxy polyethylene glycol (750 M.W.) 10 Polyethylene glycol (4000 M.W.) 2 Dithio-bis stearyl acetate 5 Isooctylphenylethoxy ethanol .2 Nonyl polyoxyethylene thioether 1 Each of these compositions was heated to between F. to F. with mixing. The composition settled to yield a clear, supernatant liquid layer on standing. The precipitated solids may be redispersed by stirring or shaking and there is a uniform distribution of the anti-tarnish agent on the solids.

EXAMPLE 4 Parts of wt.

Water 73.5 Calcined diatomaceous earth 5 Diatomaceous earth 10 Cross-linked polyethylene glycol (20,000 M.W.) 1 Polyethylene glycol (600 M.W.) 6 Dithio-bis lauryl propionate 3 Nonyl polyoxyethylene thioether 1 Polyoxyethylene sorbitol monolaurate 0.5

EXAMPLE 5 Parts of wt.

Water 77 Diatomaceous earth 9 Bentonite 1 Polyethylene glycol (4000 M.W.) 5 Dithio-bis-stearyl glycolate 5 Nonyl polyoxyethylene thioether 1 The composition of Example 1 was then applied to a first panel of a tarnished silver article. A second panel of the same article was polished with a conventional polish. Both portions of the silver surface, immediately upon being briskly rubbed with their respective polish compositions emerged bright and shining, in comparison with a third unpolished panel,

To test the tarnish preventive efiFectiveness, the protected first panel and unprotected second panel of the silver article were both exposed to hydrogen sulfide, first dried, then moist. It was found that the unprotected second panel of the silver article attained a distinct film of tarnish, while the first panel of the silver article that was protected by the surface film of the present invention remained clear and bright, similar to the condition of the metal immediately after polishing.

While the examples in the foregoing application specifically relate to silver, it should be understood that the present invention is in no way limited to an anti-tarnishing effect on silver, but rather good protection and desired cleaning elfect can be obtained on other metals, such as copper, brass and nickel, with the same formulation. Improved cleaning of these metals may be attained in a manner well known in the art with the use of a harsher abrasive and a reduction of pH through the addition of acid, such as citric acid.

From the foregoing detailed description, it will be evident that there are a number of changes, adaptations, and modifications of the present invention which come within the province of those skilled in the art. However, it is intended that all such variations not departing from the spirit of the invention, be considered as within the scope thereof as limited solely by the appended claims.

We claim:

1. An aqueous tarnish preventive metal polish composition consisting essentially of abrasive in the amount of %25% by weight, 1% to by weight dithio-bis higher alkyl ester of a lower fatty :acid selected from the group a 2a+1) b 2b-2) b 2b-2) a 2a+1) wherein 121:8-20 and b=25, water and 0.2% to about 3.5% by weight of the water soluble, nonionic wetting agent alkyl polyoxyethylene thioether Where the alkyl group contains 6-24 carbon atoms.

2. The composition of claim 1, including 0.1% to 3% of a nonionic alkylphenyl polyethoxy ethanol wherein the alkyl group contains 6-24 carbon atoms and the number of ethoxy groups is greater than 2.

3. The composition of claim 1, wherein the higher alkyl radical is stearyl.

4. The composition of claim 1, wherein the higher alkyl radical is lauryl.

5. The composition of claim 1, wherein 3% to 5% of the dithio-bis higher alkyl ester of a lower fatty acid is present.

6. The composition of claim 1, including a 120% by weight of the viscosity controller alkyloxy polyethylene glycol having a molecular weight greater than 500 and is solid at room temperature, said glycol aiding the wetting and cleaning of the metal.

7. The composition of claim 1, wherein the abrasive is present in an amount between 5% to 25% by weight.

8. The composition of claim 1 wherein b is 23.

References Cited UNITED STATES PATENTS 2,947,599 8/1960 Ennis 21-25 3,144,348 8/1964 Turbett 106-10X 3,330,672 7/1967 Kroll et al 106-3 3,362,912 1/1968 Chadwick et al 252-391 3,365,312 1/1968 Nowack 106-3 3,503,883 3/1970 Ford et a1 106-3 X 3,518,098 6/1970 Ford et al 106-3 FOREIGN PATENTS 508,855 1/1955 Canada 21-25 JOAN B. EVANS, Primary Examiner US. Cl. X.R. 

